The present invention relates to a control linkage for a suspended beam axle and in particular to a linkage that controls side to side motion of the axle as well as oscillation of the axle.
When a beam axle is used on a vehicle, such as an agricultural tractor, it is allowed to oscillate, i.e. rotate about a longitudinal axis, in which the wheel on one side of the axle moves up while the wheel on the other side of the axle moves down. The amount of oscillation is controlled by oscillation stops on the vehicle frame and the axle body that engage one another when the maximum permitted oscillation is reached. When a beam axle is provided with a suspension system, the vertical position of the axle body relative to the frame changes. The vertical movement of the axle changes the amount of oscillation permitted before engagement of the hard stops. As a result, the hard oscillation stops are removed and external means are provided to limit the oscillation. Frequently chains have been used to provide an oscillation stop with a suspended axle. An example of this is provided in U.S. Pat. No. 5,879,016. Furthermore, when a suspended beam axle oscillates, it moves from side to side, causing a phenomenon known as xe2x80x9cbounce steer.xe2x80x9d
The present invention provides a suspension linkage for an axle that provides a hard mechanical oscillation stop that moves relative to the vehicle frame as the axle travels vertically. The linkage further eliminates sideways movement of the axle that causes bounce steer. The linkage is a scissors linkage, having an upper link and a lower link joined together at a center pivot. The upper link is pivotally attached to the vehicle frame while the lower link is pivotally attached to the beam axle. The hard mechanical oscillation stops are carried by the linkage, as opposed to the vehicle frame, and thus move vertically with the axle.
Each pivotal coupling in the linkage includes thrust bearings to accommodate lateral loads. This prevents the lateral motion of the beam axle that causes bounce steer.